1. Field of the Invention
The present invention relates to a field emission device and a field emission display using the same having increased ability to focus electron beams.
2. Description of the Related Art
Displays play an important role in information and media delivery and are widely used in personal computer monitors and television sets. Displays are usually either cathode ray tubes (CRTs), which use high speed thermal electron emission or flat panel displays, which are rapidly developing. Types of flat panel displays include plasma display panels (PDPs), field emission displays (FEDs), liquid crystal displays (LCDs) and others.
In FEDs, when a strong electric field is applied between a gate electrode and field emitters arranged at a predetermined distance on a cathode electrode, electrons are emitted from the field emitters and collide with fluorescent materials on the anode electrode, thus producing visible light. FEDs are thin displays, at most several centimeters thick, having a wide viewing angle, low power consumption, and low production cost. Thus, FEDs together with PDPs attract attention as the next generation of displays.
FEDs have a similar physical operation principle to that of CRTs. Specifically, electrons emitted from a cathode electrode are accelerated and collide with an anode electrode. At the anode electrode, the electrons excite fluorescent material coated on the anode electrode to produce visible light. FEDs are different from CRTs in that the electron emitters are made of cold cathode material.
One main challenge with FEDs is to properly focus and properly control the trajectories of the electron beams emanating from the field emitters so that they land at the proper location on the fluorescent material found on the anode. Improper focus and improper control of the trajectories will cause the beams of electrons to land elsewhere and thus produce a poor image. Attempts to improve control over electron trajectories include adding a focusing gate insulating layer and a focusing gate electrode on top of the gate electrode and applying voltages to the focusing gate electrode. This was attempted in U.S. Pat. No. 5,920,151 to Barton et al where an embedded focusing structure is employed. However, the focusing gate electrode in Barton is formed on an organic material, polyimide, which requires an outgassing process for discharging volatilized gas. As a result, such an FED structure cannot be easily applied to large displays. What is therefore needed is a design for an FED that not only properly focuses the electron beams, but can also be used in large displays.